On page 49 of the latest Vintage Ford (51/6) there is an advert -
If it's for the TT why do all three columns for HIGH Direct (Speed 5) show 3.63 which is the car rear axle ratio? Should there not be a 5.17 or 7.25 somewhere??
It appears that the three columns describe slightly different internal ratios. Compared to the 'Standard' set, the H1 has the same OD ratio but a slightly higher UD.
The TT has a higher OD ratio (0.77 vs 0.83) and an intermediate UD ratio. If my sums are correct, 0.77 means that a low-ratio (7.25) TT might achieve 30mph, and a high-ratio (5.17) TT will have OD gearing only slightly lower than a normal Model T car (24mph/1000rpm).
Useful, but why doesn't the advert show this?
Why are the columns headed '....Axle Ratio'
And what is the purpose of the H1 version? Is this a 'close-ratio' speedster box?
So many questions!
Chris you are not the only one that has lots of questions on these ratios! I called Layne's about a year and a half ago and talked with a really nice young man but didn't get many questions answered.
I think that in posting this I probably answered my own questions about what the various types do, but the advert - shall we say it could be improved?